According to a first aspect, the present invention relates to a method for manufacturing a plastic fuel tank (FT) equipped with an accessory. According to another aspect, the present invention relates to a particular accessory, namely: a liquid/vapour separation capacity for a FT venting system.
Liquid tanks, when they can be moved with the liquid that they contain, are generally equipped with a venting system that guarantees environmental safety while the tank is subjected to various stresses: movements in any direction and of any amplitude, thermal stresses, underpressure and overpressure.
This requirement is encountered in the case of fuel tanks, in particular when they are mounted on motor vehicles, and it is essential to prevent liquid fuel from getting out and to manage large gas pressure and volume changes when filling the tank and throughout the time that the liquid is stored in said tank.
Solutions have been developed for solving these problems that use safety valves immersed in the tank, the upper portion of the valves passing through a wall of the tank. These valves generally open into a duct that leads to a module or canister containing a material capable of trapping the liquid vapours present in the gases, coming from the tank. However, it is not unusual for systems of this type to still have difficulties owing to the fact that, because of the particular operating circumstances, such as sudden movements or excessive high angle of tilt of the vehicle, liquid coming from the tank can nevertheless pass through the barrier of the safety valve and get into the duct leading to the canister, or even reach the latter and disturb the free flow of the vapours.
To solve this accidental carryover of liquid out of the tank, it has been sought to retain the liquid escaping via the duct leading to the canister by interposing, in this duct, a dead volume intended to act as a capacity for collecting the liquid and for letting the vapours pass freely through.
In conventional fuel systems, the aforementioned accessories (valves, capacity) are fastened to the fuel tank after it has been moulded, and pass through the wall of the tank. However, at the present time, both in Europe and throughout the world, there is a substantial tightening of the requirements regarding the limitation of pollutant emissions into the atmosphere and into the environment in general.
To limit these emissions, care is taken in particular to position the components (ventilation lines, valves, baffles, stiffeners, etc.) inside the tank and/or the fill pipe (see in particular application WO 2004/024487 in the name of the Applicant). However, when these components are fastened to the tank after it has been moulded, it is generally necessary to make at least one opening in the tank so as to be able to introduce said components into the tank and to fasten them thereto.
Therefore, the Applicant has developed a method (the subject of several pending applications) enabling these components to be easily fastened during moulding of the tank. However, the abovementioned accessories (valves, ventilation duct connecting them, liquid/vapour (L/V) separation capacity), which make up what is commonly known as the “venting line”, must be connected to the canister as explained previously. However, this canister is generally located outside of the tank and it is therefore necessary to provide a connection passing through the wall of the tank and enabling the venting line to be connected to the canister.
Such a system, with an internal venting line connected to the canister through the wall of the tank is, for example, described in U.S. Pat. No. 6,860,285. However, this document does not give any indication of the practical way for producing this connection. In fact, it is not obvious, on the one hand, how to locate, from the outside, the exact position of the end of the internal venting line to which the duct leading to the canister must be connected, and on the other hand, how to obtain a sealed connection.